The research goals for the coming year are twofold. First, microelectrode analysis of the distal segment of the optic nerve of subhuman primates will be continued. The oxygen micro-electrode measures tissue available oxygen and this may be affected by changes in the blood flow but also by oxygen utilization and hemoglobin extraction. In order to separate the various parameters the blood flow will be measured separately using micro-electrode measurement of hydrogen and the blood flow measurement technique of hydrogen washout. The tissue will be saturated with hydrogen and then the washout curve analyzed as a function of blood flow. The method is well developed for brain tisssue and should work in the optic nerve. Second, chronic glaucoma will be induced in subhuman primates by LASER destruction of their outflow channels. The early optic disk changes will be studied by electron microscopy in an attempt to correlate ultrastructural changes of the microcirculation with the physiological parameters of blood flow and oxygen availability. BIBLIOGRAPHIC REFERENCES: Stern, W.H. and Ernet, J.T.: Intracardial ophthalmic artery aneurysm. Am. J. Opth. 80:203, 1975. Ernest, J.T.: Pathogenesis of glaucomatous optic nerve disease. Tr. Am. Ophth. Soc. LXXIII, 1975.